The present invention relates generally to a lifting apparatus and more particularly to such an apparatus adapted for raising water gates and the like.
In conventional lifting apparatus used for water gates, a structure similar to that shown in FIG. 1 is employed, wherein a water gate body (c) vertically slidably disposed in a guide rail frame (b) is disposed at the outlet of water on a weir (a) and a bottom of a threaded lift stem (d) is fixed to the top of the gate body (c). The lift stem (d) is screwed on a nut (g) of an operation handle (f) disposed on a base table (e). Obviously, a reduction gear can be connected between the lift stem (d) and the operation handle (f), if desired. The water gate body (c) can be raised, held in a suspended state and lowered through operation of the screw-threaded lift stem attached thereto.
The lifting apparatus described has a simple structure and is low in cost and can stop the gate body at a desirable position without a special stopping device. Accordingly, such conventional water gate lifting apparatus have been effectively used until now with high evaluation.
However, the conventional lifting apparatus disadvantageously requires a long operation time for raising and lowering the gate body, even though it does possess such advantages as described herein. Manual operation is difficult and with the conventional lifting apparatus it is disadvantageously difficult to quickly and safely lower the gate body in times when danger of flood exists.
It has therefore been proposed to provide a lifting apparatus for a water gate body which comprises a pin rack stem connected at the top of a gate body, suitable gears for causing ascending and descending motion of the pin rack and a driving mechanism for driving these gears. Production of water gates is not significant in number and the length of a pin rack is different, depending upon the height of the gate body, according to each of the locations of the water gates. Accordingly, water gates are produced only upon receipt of orders thereof, and the productivity thereof is quite low. That is, the term for production after receipt of an order is relatively long to thus cause high cost to become a factor.
Since a lifting apparatus for a water gate body may cause a serious accident through troubles encountered in the operation thereof, it is necessary that they be produced to provide accurate and safe operation.